Do some research to determine what exercise scientists generally consider as the dimensions or components of fitness/athleticism. You will find that some believe there are five dimensions, others slightly more than that.

Select the number of dimensions that you want to measure to crown the ultimate athlete.

Explore various ways to measure each of these dimensions and select the tests that you feel are most appropriate, can be measured accurately, safely (no physical activity is completely safe but dont suggest anything too crazy), will differentiate between competitors, etc.

Thoughts:

Apply the KISS Principle: Keep it simple, stupid

If everyone scores the same, it is a bad test. If everyone, or a lot of people, score zero, it is a very bad test. Consider how you can modify it so it creates differentiation.

Is it appropriate to slightly modify the tests to accommodate women? Probably for some tests but not all.

How long does each test take?

Would order of the events matter? Would everyone go in the same order or could there be rotations or could each athlete choose their own order?

What space would you utilize? The auxiliary gyms and the green space in front of the library or more than that? Or would it all be in a gym?

I prefer that the event occur over one day, or one day for men and one for women or some other logical but limited timeframe.

In a reasonable timeframe, how many people could you accommodate with your full battery of challenges? Based on this should your event be open to anyone, to the first 100 (or fewer) who sign up, or open to one person per team/fraternity/club and so forth? Basically, what is the capacity of the event based on these tests.

Remember that we are testing for general athleticism, not sport skill. I wont accept anything with a ball, such as shooting free throws.

Prepare

For the notebook: A section with a description of each dimension of fitness, a description of each test (how do I do it?), and description of the scoring criteria.